CHARLOTTE, N.C. (CNN) - A viewer shot video Saturday afternoon which showed a car driving down Interstate 77 in Charlotte with a man clinging to the outside of the trunk, CNN affiliate WSOC reports.

Brenda Cruz was traveling with her entire family on the highway Saturday when she saw the car with the man on the back of it. She said she was worried, especially with drivers going so fast on the interstate. Troopers told WSOC-TV that they are trying to figure out what happened.

Cruz and her 17-year-old son, Samuel, couldn't believe what they saw on in I-77, just before exit seven.

"All of a sudden the kids say, 'There's someone on top of the car on the trunk,' and I'm like, 'What?'" Brenda said. "I said, 'Let me get my phone and start recording.'"

A viewer shot video Saturday afternoon which showed a car driving down Interstate 77 in Charlotte with a man clinging to the outside of the trunk, CNN affiliate WSOC reports.

Cruz said they called 911 and spoke with state troopers, who took the license plate information.

Cruz said other drivers on the road were slowing down too, watching anxiously to see what would happen to the man on the back of the fast-moving sedan.

"It was really weird. I thought it was a dummy at first," Samuel Cruz said.

Authorities received several calls but troopers said by the time they arrived the car was gone. They don't have much to go on to investigate the case.

The Cruz family said they saw the man on the back of the car break the back windshield and climb inside.

"Whenever he lifted his hand to smash the glass open it looked like it was something sharp," Samuel Cruz said.

The family said that a woman was driving the car with a child in a car seat inside.

"I'm really worried because I just hope she's OK, you know, with her kid," Samuel Cruz said.

Authorities think the incident was domestic in nature and that the driver and the man on the back of the car know each other, but they can't be sure until they track down who they are.

Troopers said it is too early in the investigation to know what, if any charges the people involved could face, but they said the driver is ultimately responsible.